Device of the kind comprising an elec-



Jan. 31, 1956 GRQENDIJK 2,733,379

DEVICE OF THE KIND COMPRISING AN ELECTRIC DISCHARGE TUBE HAVING A RIBBON-SHAPED BEAM AND UNILATERAL DEFLEC-TION Filed Sept. 12, 1951 IINVENTOR Hendrik Gro'endij By Age DEVICE OF THE KIND CONIPRISING AN ELEC- TRIC DISCHARGE TUBE HAVING A RIBBON- SHAPED BEAM AND UNILATERAL DEFLEC- TION Hendrik Groendijk, Eindhoven,

Hartford National Bank and Conn., as trustee Netherlands, assignor to Trust Company, Hartford,

The invention relates to a device comprising an electric discharge tube, in which a ribbon-shaped beam is produced, means being provided to eflect unilateral deflection of the beam. The term unilateral deflection is to be understood to mean that one of the deflecting plates has a fixed voltage impressed thereon, whereas the alterations of the deflection voltage are supplied to the opposite deflecting plate.

Although unilateral deflection has, in many cases, great advantages, it has a limitation in that, at diflerent positions of the beam greater variations of the focal distance may in general occur than in the case of bilateral deflection, in which the control-voltages are supplied to both the deflecting plates in phase opposition.

The invention has for its object to obviate as far as possible this limitation in the case of ribbon-shaped beams and to keep the focal distance for all positions of the beam as constant as possible. This is achieved, according to the invention, if in a device comprising an electric discharge tube having a ribbon-shaped beam and comprising at least a cathode, an accelerating electrode, two deflecting plates arranged opposite one another, one of which has a fixed voltage, and a collecting electrode, the deflecting plates are shaped in such a form and arranged in such a manner that in each position of the beam the variation of the spatial potential along the beam viewed from the accelerating electrode remains substantially constant in the direction of travel of the electrons.

With the conventional arrangement, in which the beam upon emerging from the aperture of the accelerating electrode, travels medially between the the variation of the spatial potential along the beam will, in the case of unilateral deflection, exhibit great diiierences for different deflection voltages and consequently for different positions of the beam.

Since only one deflecting plate is connected to the control-voltages, the spatial potential between the plates will vary unsymmetn'cally with respect to the center, so that the, variation of the spatial potential along the beam varies strongly with the deflecting voltage. Since the second derivative of the spatial potential in accordance with the length of the beam is not equal to zero, tional lens effect is produced in the deflection space, varying for diiferent values of the deflection voltages; it is strongest for those values at which the potential of the controlling deflecting plate is lower than the potential of the other deflecting plate.

The result of such an inconstant additional lens effect is that the focal distance is not constant for all positions of the beam. If the deflecting plates are shaped in such a form and arranged in a manner such that the beam travels throughout its length more closely to the fixed po tential deflecting plate than to the controlling deflecting plate, if the potential of the controlling deflecting plate drops below that of the other deflecting plate, the influence of the controlling deflecting plate connected to a nited States Patent C two deflecting plates,

varying voltage, on the spatial potential in this deflection range may be reduced to such an extent that the variation of the spatial potential, viewed from the accelerating electrode, remains always substantially constant. Thus the aforesaid additional lens eflect becomes substantially constant for all deflection Voltages, so that the focal distance remains substantially constant during the rocking movement of the beam.

In order that the invention may be more clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing, in which:

Fig. 1 shows a well-known tube construction;

Fig. 2 shows a tube construction according to the invention in a diagrammatical form;

Fig. 3 is a graph indicating the variation of the spatial potential along the beam; and

Fig. 4 shows a further embodiment of a tube according to the invention.

Referring to Fig. l, the reference numeral 1 designates the cathode, the numeral 2 a concentrating electrode, and the numeral 3 the accelerating anode. The ribbonshaped beam 7 emerging from the accelerating anode is controlled by the deflecting plates 4 and 5 and finally finds its way to one or more collecting electrodes 6. In

positive voltage of, for example, v., whereas the voltage of the deflecting plate 5 may vary between 7.0 and 230v.

The advantage of this unilateral deflection is that only the deflecting plate 5 need be supplied with a variable voltage. However, there is a limitation in that the focal distance of the beam, in this arrangement, is not constant, but it varies in accordance with the broken line 8. If the deflecting plate 5 has a low voltage, so that the beam occupies the position II, the focal distance is much smaller than, for example, at the position I, in which both plates 4 and This is due to the low potentials of the controlling deflecting the beam positions associated with potentials of the plate 5, which are equal to or higher than the fixed potential of the deflecting plate Owing to the arrangement of the deflecting plates 9 fleeting plate 9 than to the controlling deflecting plate 10. The additional lens effect is, consequently, substantially constant, so that also the focal distance is substantially constant.

As an alternative, as is indicated in Fig. 4, to use the conventional arrangement, the undesirable field variations are avoided by providing at the area where the relative distance between the deflection plates 11 and 12 is smallest, one or more auxiliary electrodes, for example, in the form of strips or rods 13, between the aperture in the accelerating anode 3 and the controlling deflecting plate 12, these rods 13 having a positive potential. These rods 13 are preferably directly connected to the deflecting plate 11.

For those cases in which it is desirable, when using a ribbon-shaped beam and unilateral deflection, that in all positions of the beam a sharp line should be projected onto the collecting electrode 6, the invention is, consequently, of importance, as for example for counter tubes, relay tubes and the like.

What I claim is:

1. A circuit arrangement comprising an electric discharge tube; said tube comprising means for producing a ribbon-shaped electron beam including a cathode and an accelerating anode having an aperture therein through which the ribbon-shaped beam emerges, collecting means for said beam spaced from said beam-producing means, and a deflection system for said beam disposed between the accelerating anode and the collecting means, said deflection system including a pair of substantially alike, opposing deflection plates each having a first portion located near the aperture in said accelerating anode and a second portion diverging outwardly from said aperture toward the collecting means; means applying positive potentials to said accelerating anode and collecting means toproduce a potential distribution therebetween, means applying a fixed positive potential to one of said deflection plates, and means applying a varying positive potential to the other of said deflection plates tending to vary the potential distribution between the accelerating anode and collecting means and thereby vary the focussing action on the beam; the portion of said other deflection plate located near the anode being spaced a greater distance from said aperture than the corresponding portion of said one deflection plate to thereby minimize the effect of the varying potential applied to said other deflection plate.

2. A circuit arrangement as set forth in claim 1 wherein the portion of said other deflection plate located near the anode is spaced a greater distance from the aperture by being bent away from said aperture.

3. A circuit arrangement comprising an electric discharge tube; said tube comprising means for producing a ribbon-shaped electron beam including a cathode and an accelerating anode having an aperture therein through which the ribbon-shaped beam emerges, collecting means for said beam spaced from said beam-producing means, and a deflection system for said beam disposed between the accelerating anode and the collecting means, said deflection system including a pair of substantially alike, opposing deflection plates each having a first portion 10- catcd near the aperture in said accelerating anode and a second portion diverging outwardly from said aperture toward the collecting means; means applying positive potentials to said accelerating anode and collecting means to produce a potential distribution therebetween, means applying a fixed positive potential to one of said deflection plates, means applying a varying positive potential to the other of said deflecting plates tending to vary the potential distribution between the accelerating anode and collecting means and thereby vary the focussing action on the beam; and a deflecting rod disposed between the first portions of. said deflection plates and between the first portion of said other deflection plate and the aperture and electrically connected to said one deflection plate to thereby minimize the effect of the varying potential applied to said other deflection plate.

4. A circuit arrangement as set forth in claim 3 wherein a pair of adjacent deflecting rods electrically connected to said one deflection plate and disposed between the first portion of said other deflection plate and the aperture are employed.

References Cited in the file of this patent UNITED STATES PATENTS 2,059,575 Gibson et al. Nov. 3, 1936 2,137,353 Schlesinger Nov. 22, 1938 2,159,818 Plaistowe et al. May 23, 1939 2,170,251 Schlesinger Aug. 22, 1939 2,449,339 Sziklai Sept. 14, 1948 2,474,224 Clark June 28, 1949 2,496,361 Sziklai Feb. 7, 1950 2,516,752 Carbrey July 25, 1950 2,539,250 Horsemann Jan. 23, 1951 2,553,735 Adler May 22, 1951 2,569,971 Ballantyne Oct. 2, 1951 2,571,723 Jonker et al. Oct. 16, 1951 2,600,142 Van Overbeek June 10, 1951 2,616,978 Jonkers et al. Nov. 4, 1952 2,617,074 De Beurs Nov. 4, 1952 

